/*
 * This file may have been modified by Bytedance Ltd. and/or its affiliates (“ Bytedance's Modifications”).
 * All Bytedance's Modifications are Copyright (2023) Bytedance Ltd. and/or its affiliates.
 */

// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#pragma once

#include <stddef.h>
#include <stdint.h>

namespace DB
{
namespace CRC32C
{
    // Return the crc32c of concat(A, data[0,n-1]) where init_crc is the
    // crc32c of some string A.  Extend() is often used to maintain the
    // crc32c of a stream of data.
    uint32_t Extend(uint32_t init_crc, const char * data, size_t n);

    // Return the crc32c of data[0,n-1]
    inline uint32_t Value(const char * data, size_t n) { return Extend(0, data, n); }

    static const uint32_t kMaskDelta = 0xa282ead8ul;

    // Return a masked representation of crc.
    //
    // Motivation: it is problematic to compute the CRC of a string that
    // contains embedded CRCs.  Therefore we recommend that CRCs stored
    // somewhere (e.g., in files) should be masked before being stored.
    inline uint32_t Mask(uint32_t crc)
    {
        // Rotate right by 15 bits and add a constant.
        return ((crc >> 15) | (crc << 17)) + kMaskDelta;
    }

    // Return the crc whose masked representation is masked_crc.
    inline uint32_t Unmask(uint32_t masked_crc)
    {
        uint32_t rot = masked_crc - kMaskDelta;
        return ((rot >> 17) | (rot << 15));
    }

}
}
